7 – Discussion

The results presented in the previous section are discussed below, in Sections 7.1 and 7.2. Table 7.1 to Table 7.5 provides a quick reference summary of the results presented in Section 6.1 and 6.2. Highly significant results will be denoted with an asterisk in the summary tables, where appropriate.

Certain considerations should be made when analysing the results. Limitations of the test sample and listening room are discussed in Sections 7.3 and 7.4. Musical considerations are outlined in Section 7.5. Finally, comments made by participants about the test material is highlighted in Section 7.6

7.1           Preference

7.1.1       Overall

  MMA vs. SFI MMA vs. SFA SFI vs. SFA
Significant? Yes*, MMA No Yes, SFA

Table 7.1 – Overall Preference

Results show a highly significant preference towards MMA when compared with SFI and parity in preference when MMA is compared with SFA. A significant preference was determined for SFA when compared with SFI. These results will be broken down on a piece by piece basis in the next section.

7.1.2       Piece 1 and Piece 2

  MMA vs. SFI MMA vs. SFA SFI vs. SFA
Significant? (Piece 1) Yes*, MMA No No
Significant? (Piece 2) Yes*, MMA Yes, MMA No

Table 7.2 – Piece 1 and 2 Preference

Results for MMA vs. SFI are consistent for each piece at a highly significant level in favour of MMA. With respect to MMA vs. SFA, the second piece shows a distinct jump in votes in favour of MMA to reach significance which indicates that the more energetic music material of the second piece has an impact on array preference. SFI vs. SFA are consistent in parity for both pieces though it should be noted that SFA was at most three votes from a significant result.

Although a single vote from significance, the overall preference results for the MMA vs. SFA back up the findings of Sungyoung et al. (2006) where the Fukada Tree tested was preferred over the Soundfield system; however, by breaking the results into each piece it can be seen that the performance characteristics have a significant impact on participant reactions.

These results are the opposite to the findings of Paquier and Koehl (2011) as their results showed that a naïve group of participants preferred the Soundfield system. However, as described in Section 2.1.3.1, the use of the Big Band would have overloaded the recording arrays. Given this, the clarity displayed by the Soundfield system in this study may explain the preference results of Paquier and Koehl (2011) in the naïve group.

7.2           Attributes

Attribute results are compiled on a piece by piece basis below. For reference, preference results are also provided. An array must achieve a result of at least 28 votes to be significant and 30 votes to be considered highly significant.

7.2.1       Multi Microphone Array vs. Soundfield ITU

  Preference Space Envelop Clarity Natural
Significant? (Piece 1) Yes*, MMA Yes, MMA Yes*, MMA Yes, SFI No
Significant? (Piece 2) Yes*, MMA No Yes, MMA No No

Table 7.3 – Piece 1 and 2 Attributes

In piece 1, the MMA was determined more spacious to a significant level; however, in piece 2, parity was achieved. It should be noted that the result is very close to being significant as the votes of an extra participant would have been enough to achieve this.

Results indicate that envelopment and spaciousness contribute to array preference as each attribute received a significant, highly significant or near significant result in favour of the preferred array in piece 1 and 2. Clarity results also indicate that a clearer sounding recording does not translate into overall preference.

7.2.2       Multi Microphone Array vs. Soundfield Adjusted

  Preference Space Envelop Clarity Natural
Significant? (Piece 1) No No No No No
Significant? (Piece 2) Yes, MMA No No Yes*, SFA No

Table 7.4 – Piece 1 and 2 Attributes

All attribute results in piece 1 result in parity though it should be noted that the envelopment result is just one vote from significance. In piece 2, clarity is highly significant in favour of SFA which shows that clarity is not a prerequisite to preference.

Interestingly, both arrays achieved a similar number of votes for spaciousness with the envelopment scores being close to significance for MMA. Indications here point towards that each array could deliver the sense of space as well as each other with the ability or inability to envelop a listener being the main difference between them.

7.2.3       Soundfield ITU vs. Soundfield Adjusted

  Preference Space Envelop Clarity Natural
Significant? (Piece 1) No No No No No
Significant? (Piece 2) No Yes, SFA No No No

Table 7.5 – Piece 1 and 2 Attributes

Parity was achieved on all comparisons except for spaciousness in piece 2 where SFA was significantly more spacious. This suggests that spaciousness was more noticeable in the more energetic music.

The SFI versus SFA comparisons shared the same front image with the rear image being the only differentiation between them, as described in Section 3.5.1. Given this, the parity results for clarity and naturalness could be influenced by the perception of the front image by participants.

With three of the four combined spacious and envelopment results being borderline between parity and significance, the influence of the rear image is indicated as being very important in the performance of an array with respect to preference. A larger test sample is likely to have benefitted these comparisons.

7.3           Test Sample Limitations

7.3.1       Sample Makeup

Where some significant and highly significant results were established it should be appreciated that the test sample was entirely comprised of people with a background and/or an education in audio. A substantial number of naïve participants could not be sourced due to the time constrains with respect to the booking of Studio D over the main listening room in the University of Salford.

Resulting from this, focus was switched to sourcing participants with a background in audio to make the best use of resources. Although the test sample could be split into naïve and expert listeners with respect to what aspect of audio they are involved in, it would have resulted in two small subdivisions of the test sample which would yield insignificant results.

Only one female volunteered to take part in the listening tests meaning that any gender based considerations were impossible to make. Similarly, the spread of participant age in the test sample also did not result in any age based considerations being possible to make.

7.3.2       Sample Size

Many of the results which were rated as parity would only have required one or two more votes to achieve significance. This translates to the votes of one extra participant. Where preference results were the main aim of the project, more definitive attribute results would have provided a better basis for further research into how the attributes contributed to the preference result. In many cases, indications based on the sample size limitations could only be speculated.

7.4           Listening Room Limitations

The University of Salford listening room, which fully complies with ITU-R BS.1116-1, was not available during the listening test time frame of February 2014 to March 2014. The use of Studio D was the best available space. Section 4.2.1 outlines the compliance of Studio D with ITU-R BS.1116-1 room standard and any areas of non-compliance should be taken into account when considering the results.

7.5           Musical Considerations

This project focused on the recording of a classical quartet, therefore any extrapolations on the suitability of the recording arrays used in this project for the recording of other types of music must be taken with care. An aim of this project is to add to the body of knowledge in this subject area. Further work can add to this knowledge by testing with different musical ensembles and different performance spaces.

The project greatly benefitted from the services of a professional string quartet. This meant that the resulting musical extracts were of a high quality. Additionally, the offer and use of the Queen’s University Belfast microphone and recording equipment meant that the recording signal chain was also of a very high quality, as was the Harty Room performance space. All these aspects must be considered in any future work as a weak element in these areas cannot be fixed without re-recording.

7.6           Participant Comments

Participants were offered an opportunity to give further information on their thoughts and opinions about each pairwise comparison in their own words. Although this information cannot be seen as conclusive and cannot be used as the basis of project conclusion, the comments do correlate to the preference and attribute results while also offering an interesting insight into participant’s thoughts.

Some participants noted that the Multi Microphone Array felt more natural, spacious and warm sounding while at times lacking instrumentation detail. Some felt the Soundfield Adjusted extracts sounded thin and harsh with others feeling that this aspect allowed them to pick apart instruments more clearly but the latter did not necessarily translate into preference for the Soundfield based extract. One participant felt that the Soundfield Adjusted extract felt heavily processed compared with the multi microphone extract. Some participants also felt that the front to rear correlation was too high in the Soundfield extracts.

Next post

8 & 9      Conclusions & Further Work.

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